Philippine President Rodrigo Duterte said Thursday that Japanese Prime Minister Shinzo Abe asked him to explain his anti-American rhetoric during summit talks.

The acid-tongued Duterte has launched repeated tirades against the United States and President Barack Obama for criticising his deadly crime war, which has claimed more than 3,800 lives in nearly four months.

Duterte’s comments, backed by repeated praise for China, have thrown into doubt the Philippines’ 70-year alliance with the United States.

Japan is one of the other top US allies in Asia, and Duterte said Abe had raised the issue with him in a meeting the previous day in Tokyo.

“Yes, of course,” Duterte told reporters when asked if Abe had asked for clarification about his criticisms of the United States.

“I told him they were mere words. Why would you give these things any importance,” Duterte said in the port city of Yokohama, southwest of Tokyo, where he observed Japanese coast guard rescue drills.

However, Duterte said he then repeated his anti-American grievances to Abe, including that Washington unfairly raised human rights concerns and treated the Philippines like a “dog”.

US officials have said they are baffled about Duterte’s comments, but point out that none of his rants have been backed up by concrete policies.

Duterte has also repeatedly given contradictory or confusing positions on the United States.

On a state visit to Beijing last week, Duterte announced the Philippines’ “separation” from the United States and declared his support for China.

But immediately after returning home, Duterte walked back from those comments, saying he would not sever US relations.

Duterte has used his three-day trip to Japan to highlight close economic and investment ties, and has gone out of his way to praise the country and its people.

A scheduled meeting between Duterte and Emperor Akihito was cancelled Thursday due to the death of his 100-year-old uncle Prince Mikasa.